Just for filling pin holes, any kind of spot putty would work. If you got a coat of primer on it to show you where the pinholes holes are, we are only talking about a little dot or putty here and there. That's what spot putty is for. Plastic modelers have it available in some military colors even and it comes in smaller tubes. Hell, even old Pactra plastic balsa would work for this. I would not use spackling compound. It's vinyl usually.
Type at you later,
Dan McEntee